Blood tests can be challenged on numerous grounds in California DUI cases. There are specific methods that must be followed in extracting, storing, moving, and testing blood samples. There are personnel and lab qualifications that must be met. There are many issues surrounding blood samples that can be brought to light. We will mention some of these issues.
The person extracting the blood sample must be qualified. Not just anyone can draw blood.
Assuming we have a qualified person, then there are a multitude of steps that have to be followed. If they are not properly followed, depending on the facts and the Judge, the evidence may be excluded, or the jury may view it as less than reliable.
A non-alcohol based swab must be used to sterilize the puncture site. If an alcohol swab is used, that alcohol will enter the needle and become mixed with the blood sample. That will give a false high reading.
The blood should be drawn from a vein, as opposed to an artery, into a vial. There has to be a sufficient amount of blood drawn, and it must be properly mixed with sufficient amounts of preservatives and anti-coagulants. Just in re-reading the previous sentence you can get a sense of all the potential issues that may arise from the beginning stages of a blood draw. The best DUI defense attorneys examine proof of every single step: if any one of these requirements isn't met, it is possible to get your blood test thrown out (that is, excluded or suppressed instead of used against you).
Assuming a qualified person (e.g., nurse, phlebotomist, etc.) properly prepped the extraction area and then extracted from a vein a sufficient amount of blood into a proper-sized, non-expired vial — such as a gray-topped 10 milliliter vial that contains sufficient amounts of preservatives and anti-coagulants — and then sealed the vial and properly mixed the contents of the vial (by inverting it 8 times), then that vial must be labeled correctly, stored, and transported for testing.
If the vial of blood is not labeled correctly, then the results have to be excluded because they may not belong to the subject.
If the vial is not stored at the correct temperature, that will cause natural fermentation to accelerate, again leading to a higher blood alcohol content reading.
Chain of custody has to be proven by the prosecution. The prosecution has to show that the location or whereabouts of the sample has been accounted for at every step so as to tie the blood sample to the defendant. If the prosecutor can't prove the blood was properly handled, a good defense attorney will keep the blood test result from ever being used again you.
The quantity of blood that is extracted will be enough to allow a portion of it to be tested by the government and a portion of it to be preserved for testing by the defense. If blood is missing, or none is preserved for the defense to conduct its own testing, the prosecution has to explain why that is the case.
There are times when retesting may be appropriate, but if the defense is based on contaminated blood, then a retest is useless and should not be undertaken.
Assuming the blood was not drawn properly — or that no measures were taken to slow down the natural fermentation process, or certain errors were committed that contaminated or fermented that specific sample — by the time the sample reaches the government’s lab for testing, the contamination or fermentation has already caused issues with the blood sample.
Because the contamination had already occurred before the government tested the sample, any subsequent testing of that contaminated sample will yield an improper or unreliable result. In other words, since the sample was compromised or bad, a retest is not going to fix or address the problematic blood sample. Again, your DUI defense attorney should work to prove that the sample, therefore, cannot be used as evidence against you.
The above list is not exhaustive. Depending on the facts of the case other defenses may be available.
The only way to determine whether any potential defense exists is to actually roll up the sleeves and get to work on finding them.
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